AT&T Inc.
T -0.24%
Monday said its practice of exempting its own streaming video services from data-usage caps for its wireless customers complies with the law and benefits consumers, in a response to concerns from a federal regulator.

The Federal Communications Commissionsent a letter to AT&T almost two weeks ago over worries the practice, known as zero-rating, “may obstruct competition and harm consumers.”

“These initiatives are precisely the kind of pro-consumer challenges to cable that the Commission heralded in approving AT&T’s acquisition of DirecTV,” wrote
Robert Quinn,
AT&T’s policy chief, in a letter to the agency Monday. AT&T acquired satellite-TV operator DirecTV last year.

The Dallas telecom giant, which agreed to buy
Time Warner Inc.
for $85.4 billion last month, began zero-rating its DirecTV video app in September. Mr. Quinn said nearly three million consumers used the app in the first four weeks after its launch. AT&T plans to offer the same treatment for its over-the-top service DirecTV Now launching this month.

The FCC contends the practice could deter consumers from accessing existing and future mobile video services not affiliated with AT&T. The company has said that it offers any company that wants to be zero-rated the same payment terms available to DirecTV.

An FCC spokesman said the agency is reviewing the response and declined to comment further. The agency sent the letter a day after President-elect
Donald Trump’s
victory and last week Republican congressional leaders asked the FCC to stop taking controversial regulatory actions until the new administration is on board. That suggests that the FCC may not be able to take any further steps on the AT&T matter.

While critics regard zero-rating as a way of skirting net-neutrality rules that require internet-service providers to treat all traffic the same, AT&T said it “faithfully adhered” to those rules in starting the program, which is “consistent with decades of commission precedent.”

Mr. Quinn said any FCC position to the contrary would be a “radical departure from established law.”

AT&T began allowing companies to pay for zero rating in 2014, but so far no major streaming providers have done so.
Verizon Communications Inc.
doesn’t charge its customers for data for its National Football League games or its go90 mobile video app.

T-Mobile US Inc.’s
“Binge On” program allows any video provider to be exempt from data caps without paying the carrier, although the video is delivered at lower quality. It also allows customers and content companies to opt out.